The issue was that best_extension_by_limited_search() had to go through
too many plans with the same cost as there where many EQ_REF tables.

Fixed by shortcutting EQ_REF (AND REF) when the result only contains one
row. This got the optimization time down from hours to sub seconds.

The only known downside with this patch is that in some cases a table
with ref and 1 record may be used before on EQ_REF table. The faster
optimzation phase should compensate for this.

Before this change the test could abort with ER_OPTION_PREVENTS_STATEMENT

The solution is to initialize field_ref_zero in main_low() before
xtrabackup_backup_func() and xtrabackup_prepare_func() calls.

MDEV-28446 mariabackup prepare fails for incrementals if a new schema is created after full backup is taken

Adding a 10.6 specific test

Errors where:

/buildbot/amd64-ubuntu-2004-msan/build/sql/item.h:6478:12: error: 'val_datetime_packed' overrides a member function but is not marked 'override' [-Werror,-Winconsistent-missing-override]
  longlong val_datetime_packed(THD *thd)
           ^
/buildbot/amd64-ubuntu-2004-msan/build/sql/item.h:3501:12: note: overridden virtual function is here
  longlong val_datetime_packed(THD *thd) override;
           ^
/buildbot/amd64-ubuntu-2004-msan/build/sql/item.h:6480:12: error: 'val_time_packed' overrides a member function but is not marked 'override' [-Werror,-Winconsistent-missing-override]
  longlong val_time_packed(THD *thd)
           ^
/buildbot/amd64-ubuntu-2004-msan/build/sql/item.h:3502:12: note: overridden virtual function is here
  longlong val_time_packed(THD *thd) override;
           ^

remove AIX support, as 10.4 is not tested on AIX, so cannot test a regex

Fixed failing main.default on Windows
(to trigger an assert the test needed a debug build without
safemalloc, as 0xa5 happened to have the important bit set "correctly")

Test compat/oracle.sp-package-mysqldump needed re-record.

MDEV-21810 MBR: Unexpected "Unsafe statement" warning for unsafe IODKU

MDEV-17614 fixes to replication unsafety for INSERT ON DUP KEY UPDATE
on two or more unique key table left a flaw. The fixes checked the
safety condition per each inserted record with the idea to catch a user-created
value to an autoincrement column and when that succeeds the autoincrement column
would become the source of unsafety too.
It was not expected that after a duplicate error the next record's
write_set may become different and the unsafe decision for that
specific record will be computed to screw the Query's binlogging
state and when @@binlog_format is MIXED nothing gets bin-logged.

This case has been already fixed in 10.5.2 by 91ab42a8 that
relocated/optimized THD::decide_logging_format_low() out of the record insert
loop. The safety decision is computed once and at the right time.
Pertinent parts of the commit are cherry-picked.

Also a spurious warning about unsafety is removed when MIXED
@@binlog_format; original MDEV-17614 test result corrected.
The original test of MDEV-17614 is extended and made more readable.

or slow query log when the log_output=TABLE.

When this happens, we temporary disable by changing log_output until
we've created the general_log and slow_log tables again.

Move </database> in xml mode until after the transaction_registry.

General_log and slow_log tables where moved to be first to be dumped so
that the disabling of the general/slow queries is minimal.

Previously the correct SQL mode for a stored routine or
package was only set before doing the CREATE part, this
worked out for PROCEDUREs and FUNCTIONs, but with ORACLE
mode specific PACKAGEs the DROP also only works in ORACLE
mode.

Moving the setting of the sql_mode a few lines up to happen
right before the DROP statement is writen fixes this.

fil_crypt_flush_space(): Correct a condition that was refactored
incorrectly in commit aaef2e1d

MDEV-28402 ASAN heap-use-after-free in create_tmp_table, Assertion `l_offset >= 0 && table->s->rec_buff_length - l_offset > 0'

Make default() function follow Item_field and use get_tmp_table_item() for
change_to_use_tmp_fields().

This is based on commit 20ae4816
with some adjustments for MDEV-12353.

row_ins_sec_index_entry_low(): If a separate mini-transaction is
needed to adjust the minimum bounding rectangle (MBR) in the parent
page, we must disable redo logging if the table is a temporary table.
For temporary tables, no log is supposed to be written, because
the temporary tablespace will be reinitialized on server restart.

rtr_update_mbr_field(), rtr_merge_and_update_mbr(): Changed the return
type to void and removed unreachable code. In older versions, these
used to return a different value for temporary tables.

page_id_t: Add constexpr to most member functions.

mtr_t::log_write(): Catch log writes to invalid tablespaces
so that the test case would crash without the fix to
row_ins_sec_index_entry_low().

row_ins_sec_index_entry_low(): If a separate mini-transaction is
needed to adjust the minimum bounding rectangle (MBR) in the parent
page, we must disable redo logging if the table is a temporary table.
For temporary tables, no log is supposed to be written, because
the temporary tablespace will be reinitialized on server restart.

rtr_update_mbr_field(): Plug a memory leak.

In SELECT_LEX::update_used_tables(),
do not run the loop setting tl->table->maybe_null
when tl is an eliminated table

(Rationale: First, with current table elimination, tl already
 has maybe_null=1. Second, one should not care what flags
 eliminated tables had)

(This is the assert that was added in fix for MDEV-26047)

Table elimination may remove an ON expression from an outer join.
However SELECT_LEX::update_used_tables() will still call

  item->walk(&Item::eval_not_null_tables)

for eliminated expressions. If the subquery is constant and cheap
Item_cond_and will attempt to evaluate it, which will trigger an
assert.
The fix is not to call update_used_tables() or eval_not_null_tables()
for ON expressions that were eliminated.

As Travis is not used anymore for CI is not wise to keep untested CI files laying around
that someone can base their effort to update un-used files.

Debian script debian-start upgrades database (which can be huge)
and prints lots of unnecessary information (not errors). Add
'--silent' to only sport possible errors

* FreeBSD returns errno 31 (EMLINK, Too many links),
  not 40 (ELOOP, Too many levels of symbolic links)
* (`mysqlbinlog|mysql`) was just crazy, why did it ever work?
* socket_ipv6.inc check (that checked whether ipv6 is supported)
  only worked correctly when ipv6 was supported
* perfschema.socket_summary_by_instance was changing global variables
  and then skip-ing the test (because on missing ipv6)

MDEV-28391: table_exists procedure fails when arguments contain escaped backticks as an quoted identifiers

- When arguments to the procedure contain quote in the name, procedure fails with parsing error.
  The reason was because additional quoting is done when testing TEMPORARY table with the same name.
- Reviewed by: <wlad@mariadb.com>

Window Functions code tries to minimize the number of times it
needs to sort the select's resultset by finding "compatible"
OVER (PARTITION BY ... ORDER BY ...) clauses.

This employs compare_order_elements(). That function assumed that
the order expressions are Item_field-derived objects (that refer
to a temp.table). But this is not always the case: one can
construct queries order expressions are arbitrary item expressions.

Add handling for such expressions: sort them according to the window
specification they appeared in.
This means we cannot detect that two compatible PARTITION BY clauses
that use expressions can share the sorting step.
But at least we won't crash.

MDEV-17843 Assertion `page_rec_is_leaf(rec)' failed in lock_rec_queue_validate upon SHOW ENGINE INNODB STATUS

lock_validate() accumulates page ids under locked lock_sys->mutex, then
releases the latch, and invokes lock_rec_block_validate() for each page.
Some other thread has ability to add/remove locks and change pages
between releasing the latch in lock_validate() and acquiring it in
lock_rec_validate_page().

lock_rec_validate_page() can invoke lock_rec_queue_validate() for
non-locked supremum, what can cause ut_ad(page_rec_is_leaf(rec)) failure
in lock_rec_queue_validate().

The fix is to invoke lock_rec_queue_validate() only for locked records
in lock_rec_validate_page().

The error message in lock_rec_block_validate() is not necessary as
BUF_GET_POSSIBLY_FREED mode is used to get block from buffer pool, and
this is not error if a block was evicted.

The test case would require new debug sync point. I think it's not
necessary as the fixed code is debug-only.